Hearing-aid users often complain of poor sound quality and difficulty understanding speech in noisy situations. The current standard of care, acoustic hearing aids, cannot restore audibility across the whole frequency spectrum of hearing because technical constraints severely limit acoustic amplification above 4-5 kHz. A prototype EarLens Photonic Hearing System (PHS) was designed and built to allow subjects to hear amplified sounds from 125 Hz up through 10 kHz. The system is comprised of two components: a PhotoKinetic Contact Transducer (PKCT) that directly vibrates the eardrum upon receiving power and signal through a wireless light and a Behind-The-Ear sound processor (BTE) that processes incoming sound and transmits the light. An FDA-approved IDE study has demonstrated the safety, performance, and feasibility of users to benefit from the extended-bandwidth PHS. The proposed multi-site definitive clinical study will provide the safety and performance data required for regulatory approval in the US. The study will be conducted on a total of 80 subjects with mild-to-moderate hearing impairment. 20 subjects will be enrolled at each of four external clinics. The study protocol involves the following steps: (1) Screening, Enrollment, and Unaided Audiometric and Performance Testing; (2) PHS fitting; (3) PHS Audiometric and Performance Testing; (4) PHS Removal; and (5) Study Exit. Outcome measurements will be made with regard to: (A) safety; (B) air-conduction audiometric thresholds; (C) speech-understanding thresholds under quiet conditions and in the presence of noise and speech maskers; and (D) assessment questionnaires to examine self-perceived benefit and quality-of-life improvements. PHS aided measurements will be performed after initial fitting and at the end of the four-month study period. Measurements B-D will also be made using the subjects' own acoustic hearing aids, as applicable, to determine benefit of the PHS over the current standard of care. The significance of having an extended-bandwidth assistive hearing device on the market in the US is that such a system will, for the first time, allow individuals wih mild to moderately severe hearing impairment to benefit from the improvements in sound quality and speech-discrimination ability that become possible when high-frequency acoustic cues are clearly perceived. Such advancement in hearing technology may lead to increased adoption rates for hearing devices, which would help to relieve communication difficulties and improve the overall quality of life for those affected by hearing loss.